Of the many minerals that may affect thyroid function, iodine is the most important. It is an essential building block for thyroid hormones and interacts with the function of the thyroid gland. Iodine is also important for supporting a healthy metabolism, aiding in growth and development, and preventing certain chronic diseases.
Iodine deficiency used to be the leading cause of hypothyroidism and an abnormally enlarged thyroid gland (called a goitre) and still remains so in certain regions. A goitre occurs in response to the body trying to “trap” as much iodine within the bloodstream as it can. Iodine is also absorbed and stored within tissue in many other organs, including the stomach, brain, spinal fluid, skin and certain glands.
However, Hashimoto’s is not associated with an iodine deficiency. There is a question of whether iodine should be supplemented for those with Hashimoto’s. Because iodine stimulates production of TPO, could this in turn stimulate levels of TPO antibodies, indicating an autoimmune flare-up.
Some health experts claim that iodine deficiency is the cause of thyroid disorders and that iodine supplements will resolve them. Others say that iodine excess can cause thyroid disorders and that taking iodine will make them worse. The truth may lie somewhere in the middle. This may be because Iodine, like Iron, has a narrow window where it’s therapeutic, with deficiency and excess can both affect the thyroid negatively.
In 1999, a study including 377 people with Hashimoto’s found that a combination of thyroid hormones and a daily dose of up to 200mcg of Iodine per day were found to reduce thyroid antibody levels. This study showed that a low dose of iodine on a daily basis is usually not going to be problematic for people with Hashimoto’s, and in fact may be beneficial.
A reduction in the amount of naturally iodine-rich foods in people’s diets (wild-caught fish, green vegetables and sea vegetables, for example), a higher exposure rate to certain chemicals found in processed foods that reduce iodine absorption (especially the compound called bromine, found in many plastic containers and baked goods, for example), make consuming very high levels from iodine-rich foods alone very unlikely. Real salt, either Himalayan or Celtic sea salt, as opposed to iodized table salt, contains more than 60 trace minerals and doesn’t pose a risk for overconsuming iodine like table salt does. It’s also much more natural, beneficial and tastes better.
Risk factors for iodine deficiency include consuming foods grown in low-iodine soil, not consuming many seafoods, not using iodized salt, and not using iodine supplements or iodine-containing multivitamins. Isoflavones derived from soy also bind to iodine and prevent its utilization for the production of thyroid hormone. Fluoride and bromine compete with iodine for transport and utilization. Fluoride is found mainly in toothpaste and fluoridated water. Bromine is found multiple products such as plastics, baked goods, sodas, flame retardants and insecticides.
Selenium works in tandem with iodine and is involved in the recycling of iodine in the body. Therefore, selenium supplementation should also be considered when taking iodine.
Bottom line; Iodine increases thyroid function if the individual is iodine deficient – Iodine decreases thyroid function if the individual is sufficient. Every patient could benefit from a thorough evaluation of their iodine levels.
In the case of a deficiency of iodine, I do recommend iodine supplements but only in the dose range found in multivitamins and prenatal vitamins (most contain between 150 mcg–220 mcg). If you are deficient in iodine, an iodine supplement will likely help your symptoms and may improve your outcomes. A multi vitamin would also contain other important minerals such as selenium and zinc.